Coated glass fiber and method of making



objects. Especially when in the United States Patent OfiFice 2,754,223 COATED GLASS FIBER AND METHOD OF MAKING Remus F. Caroselli, Manville, R.-I., assignor to Owens- Corning, Fiberglas Corporation, a corporation of Delaware No Drawing. Application January 24, 1952, Serial No. 268,147

16 Claims. (Cl. 117- 54) This invention relates to a new and improved treatment for glass fibers and fabrics formed thereof and it relates more particularly to glass fibers characterized by increased abrasion resistance and to a method for producing same;

Because of their high strength and flexibility coupled with their relative inertness, glass fibers have become widely adopted as an important component in structural materials, reinforced plastics, coated fabrics, or in their more available forms as strands, yarns, cords and textile fabrics and the like. In each of these uses where glass fibers are not directly combined with resinous material, as in reinforced plastics or coated fabrics,it has been found necessary to supplythe fibers with a protective coating, otherwise they would be subject to destruction by mutual abrasion or by abrasion with other surfaces and form of yarns, strands or fabrics, abrasion resistance and the method for securing same become controlling factors in the life and in the use of the glass fiber products. In the past, it has been difiicult to secure sufiicient abrasion resistance without loading the fibers with so much protective coating as to render the fibers stifi whereby the cords, yarns or fabrics produced therefrom become harsh and unfit for many uses and applications.

It is an object of this invention to produce glass fibers, yarns, cords and fabrics characterized by high abrasion resistance and it is a related object to provide a simple method for producing the same.

Another object is to produce and to provide a method for producing glass fibers and fabrics providedwith a protective coating which imparts exceptionally high abrasion resistance informing and in the final product while at-the same time improving the hand, softness, smoothness and draping qualities of the fabric.

To the present, use has been made to a great extent of a butadiene-acrylonitrile copolymer and of polyacrylates asa protective coating to impart abrasion resistance to glass fibers. In the recently developed techniqne for heattreatment to relax and weave-set the glass fibers whileinfabric form, asdescribed in the copendingappli: cations of Waggoner et al., Serial Nos. 91,841; 91,842 and91,843, filed on Ma 6, 1949, all now abandoned, butadiene-acrylonitrile copolymer or polyacrylate compositions have been applied alone or in combination with a chrome complex of the type described by Her Patents Nos. 2,359,858 and 2,381,752 to protect the fibers against destruction'by abrasion forces'an'd to produce a" fabric having silky softness and good band.

A further object is'to produce and to provide a method for producing glass'fibers coated with acomposition to inrprove abrasion resistance and which is improved in many respects by Washing or otherwise handling the fabric in the manner for which it was intended.

A still further object isto provide'a method for improving the softness, feel and wrinkleproofnes'sof a fabiic'which has been coated in the manner herein described to improve its abrasion resistance:

therewith in finely divided form.

It has been found that the abrasion resistance of glass fibers and fabrics formed therefrom can be markedly increased 7 over anything which has heretofore been achieved by treating the fibers from which all previous coatings have preferably been removed with a composition containing a butadiene-acrylonitrile copolymer in combination with polytetrafiuor'oethylene resin dispersed The materials should be present in the fibrous structure in amounts ranging from O.1 to 5 percent by weight polytetrafluoroethylene and 0.2 to 25 percent by weight butadiene-acrylonitrile copolymer.

The two components which make up the treating composition are of substantially dissimilar character but they cooperate in a manner to introduce the desired improved abrasion resistance without impairing the softness, silkiness and good draping qualities which have heretofore characterized fabrics treated in accordance with the cited Waggoner et al. applications, previously referred to for relaxation and weave setting of the glass fibers of the fabric. On the one hand, the butadieneacryloiiitrile copolymer functions as a film former upon drying to coat the fibers substantially completely throughout their lengths. On the other hand, the polytetrafluoroethylene is selected to be incapable of fusion at the temperatures of tre'atment'for' drying or for forming the butadiene-acrylonitr' e copolymer into a film and therefore remains in particle form dispersed throughout the butadiene-acrylonitr'ile copolymer in the treating composition and in the film which' is formed upon the glass fiber surfaces ofi'd'rying, When applied to the glass fiber surfaces, as a size in forming, the dispersed particles of polytetrafluoroethylene appear to act asball bearing surfaces and facilitate relative movement between fibers without abrasion. For example, with most glasses and especially with lead glass, the twistingefficiency of fibers in strand and yarn formation sized in accordance with this invention is markedly increased and in most instances practically doubled. In their final stage, the discrete particles of polytetrafluoroethylene appear to be anchored into the continuous film of the butadiene-acrylonitrile copolymer but the exposed portions of the particles continue to act as bearing surfaces and lubricants to improve the draping qualities, softness and hand of the fibers and fabric formed-thereof. The particles of polytetrafluoroethylene function in addition positively to increase the toughness and the abrasion resistance of the composite coating;

The treatingcomposition is preferably applied with the particles of polytetrafluoroethylene dispersed in a latex of the butadiene-acrylonitrile copolymer. The concentration of solids within the ratio prescribed depends upon the form of the fibers being treated and the amount thereof which it is desired to have deposited on the glass fiber surfaces. When applied onto heat cleaned glass fiber fabrics or when applied to textile fabrics of glass fibers following the heat treating step of the relaxing weave setting process of the Waggoner et al. application, previously referred to, compositions containing 5-25 percent solids may be used.

The improvement in abrasion'res'istance and inmany other characteristics of glass fibers by'applicationof the butadiene acrylonitrile copolymer and polytetrafiuoroethylene'in particle form is not limited to textile'fabrics' of glass fibers. Marked increase in abrasion resistance and improved efficiency'in fiber handling alsoresult when the individual filaments of glass fibers are treated in forming or when strands, yarns, or other bundles of glass fibers are treated after forming but preferably after the size previously applied'has' beenremoved from the'surfa'ces thereof-as by washing orheat cleaning. When'applied asa' size onto glass filaments in forming, a composition removes excess composition containing considerably lower concentrations of butadiene-acrylonitrile copolymer and polytetrafiuoroethyene may be used, such for example as compositions containing 15 percent by weight solids within the ratio previously set forth. For the treatment of strands, yarns or bundles, the solids may range through the span of 1 percent by weight up to 25 percent by weight, depending upon the use to be made of the treated fibers.

When applied in forming, application may be made by means of a wiping pad or roll applicator as the individual filaments are gathered together and formed into strands. When treatment is to be made of strands or yarns of twisted or intertwisted fibers, as in the manufacture of tire cord or textile treads, application may be made by passing the strand, yarn, or cord through a bath of the treating composition and then through a die which followed by passage through a drying oven for removal of the diluent by volatilization and setting of the butadiene-acrylonitrile copolymer into a continuous film in which the unfused particles of polytetrafiuoroethylene become embedded. When applied onto an already formed fabric, as for example upon following the heat treating step described in the applications previously referred to in the Waggoner et al. processes, the composition may be padded or otherwise applied by conventional means onto the fabric followed by drying at a temperature within the range of 250-400 F. or higherso long as the temperature is not sufficient to cause fusion of the particles ofpolytetrafluoroethylene.

Although the components may be formulated into a cationic dispersion for application onto the glass fibers whereby the positively charged particles orient with the negative groups that predominate in ordinary glass, it has been found possible and it is preferred to formulate the ingredients into an anionic dispersion whereby the particles become negatively charged for orientation with positive groups having different sites in the surfaces of the glass fibers to provide a new and improved anchorage which is especially desirable in fibers and fabrics formed of lead glass and the like.

Further improvement in the characteristics of the fibers or fabrics treated in accordance with the practice of this invention may be secured when such fibers or fabrics are subsequently treated with a Werner complex compound of the type wherein an acido group having more than carbon atoms is coordinated with a trivalent nuclear chromium atom, such for example as compounds described in the aforementioned Iler patents. Lubricating compounds of the type described are represented by stearato chromic chloride or tallow acid chromic chloride and the like. Application from water solutions containing from 0.1 to 2 percent by weight of the chrome complex may be made by a padder or other conventional means and the complex insolubilized on the glass fiber surfaces by drying preferably at an elevated temperature, such as 250450 F.

By way of illustration, but not by way of limitation, the following examples are given to illustrate the practice of this invention:

Example 1 In the preparation of a 50 gallon batch of treating composition, 8 pounds of an anionic suspensoid containing 50 percent by weight polytetrafluoroethylene in finely divided form is incorporated with stirring into about 25 gallons of water. 80 pounds of an anionic latex containing 40 percent by weight butadiene-acrylonitrile copolymer is introduced with agitation and then the mix is diluted with water up to 50 gallons. The composition contains about 1 percent by weight polytetrafluoroethylene and about 7 percent by weight butadiene-acrylonitrile copolymer.

The composition is padded onto a glass fiber fabric after it leaves the oven used in carrying out the heat treating step of the cited Waggoner et a1. processes. wherein the glass fibers in fabric form are heated at a temperature ranging from 1050 to 50 below the fusion temperature of the glass composition of which the fibers are formed for at least a few seconds at the higher temperature to a few minutes at the lower temperature whereupon the size originally applied to the glass fiber surfaces is burned off at an early stage of the heat treating process and the glass fibers are relaxed and weave set in their fabric form, and then the heat treated fabric is cured at a temperature of about 300 F. A composition containing about 1 percent by weight stearato chromic chloride is padded onto the fabric which is again dried at a temperature of about 300 F.

Example 2 An anionic dispersion containing 1.5 percent by weight polytetrafluoroethylene in finely divided form and 3.5 percent butadiene-acrylonitrile is wiped as a size onto a plurality of glass fiber filaments as they are attenuated from continuous strands of molten glass and gathered together into strands. The formed strands are wound upon drums and later a number of such strands may be twisted or intertwisted into a cord or into yarns for fabric formation.

When the filaments are coated with a composition of the type described and twisted into yarns, it has been found that the twisting efficiency is greatly increased to almost double the values previously secured with other treating compositions. Before or after the yarns are woven into a fabric, it is preferred to heat the fibers at a temperature of about 350 F. in order to make certain that the butadiene-acrylonitrile copolymer has been transformed into a film in which the unfused particles of polytetrafiuoroethylene become anchored to lubricate the fibers and toughen the coating. When in the form of a cord or fabric, the fibrous structure may be treated with the stearato chromic chloride and then dried at a temperature ranging from 250350 F.

A composition of the type described by this example is particularly well adapted for use with glass fibers formed of a melt of lead glass in which more than 50 percent of the melt is formed of lead oxide.

Instead of butadiene-acrylonitrile copolymer, other film forming materials capable of dispersion in aqueous medium and providing an adherent base upon drying may be used in corresponding proportions and amount with polytetrafluoroethylene. Excellent results, for example, have been secured with the combination of polytetrafluoroethylene and a polyacrylate of the type butyl methacrylate or a polyacrylate emulsion sold commercially under the trade name Hycar PA by the B. F. Goodrich Chemical Company. Use may also be made of a latex formed of butadiene-acrylonitrile coplymer compounded with 50-75 percent by weight styrene and marketed under the trade name X-512. by the Dow Chemical Company of Midland, Michigan, or use may be made of polyvinyl acetate or the like thermoplastic resinous materials. Though less desirable, adherent bases for anchorage of the particles of polytetrafluoroethylene may also be secured by compounding with rubber-like material including buna-S or natural resins, starchy gelatins, proteins, gums and the like.

Example 3 An aqueous emulsion of 10 percent Hycar PA containing about 50 percent polyacrylate and about 8 percent of a 50 percent dispersion of polytetrafluoroethylene in finely divided form is padded onto a glass fiber fabric just after it emerges from the heat treating oven of the Waggoner et a1. processes previously referred to. The fabric is then heated at 300 F. and coated with a 2 percent solution of stearato chromic chloride followed by curing at about 300 F. v

A textile fabric treated in accordance with this example exhibits vast improvement in abrasionresistance compared with a similar fabric treated in the usual manner with Hycar PA followed by the stearato chromic chloride. The improvement is illustrated by the following results secured in the two types of treatment with a fabric designated as 138:

Polyacrylate Polyacrylate plus poly tetrafiuoroethylene Schieter abrasion 2, 735 382, 940 Rod abrasion (warp) 12, 855 96, 377 Flexure endurance (warp 88, 808 205, 545

Example 4 In the manufacture of tire cord, intertwisted yarns of glass fibers, after heat'cleaning, are passed through a bath in the form of a dispersion containing 15 percent by Weight butadiene-acrylonitrile copolymer and 3 percent by weight polytetrafiuoroethylene in particle form. The cord is passed up through a die located over the bath f remove excess of the composition and from the die, the cord is threaded through a baking oven maintained at a temperature between 300 and 350 F. to drive off the diluent and cure the film forming material. Where anchorage is desired to rubber or other elastomer in tire manufacture or in the manufacture of coated fabrics, the treated cord may be passed through a bath containing a small percentage (0.5 to 2.0 percent by weight) of a chromic chloride having an unsaturated acido group coordinated with the trivalent nuclear chromium atom, such for example as methacrylato chromic chloride, followed by heat treatment at about complex.

By Way of still further modification to secure further improvement in the characteristics of the treated fabric, it has been found that the softness and suppleness of the fabric is enhanced after treatment in the manner described or even after treatment in the manner previously employed when the fabric is subsequently washed vigorously as by mechanical means to break up the film on the glass fiber surfaces. It appears that such film rupture by Washing eliminates the harshness which often characterizes such coated fibers and fabrics Without noticeable reduction in the strength, abrasion resistance and like properties of the fabric.

Where color is desired, suitable organic dyes may be added to the butadiene-acrylonitrile copolymer or other film forming material of the type heretofore described and polytetrafiuoroethylene treating composition or else such dyes may be applied afterwards in the usual manner for coloring fabrics since the fibers having the butadiene-acrylonitrile copolymer and polytetrafluoroethylene, with or without the chrome complex, appear to be highly receptive to such coloring agents and provide sufiicient anchorage therefor to retain the color substantially permanently. Suitable dyes for use in coloring fibers include the direct dyes of the type Methylene Blue, Fast Red A, or the mordant dyes of the type Alizarin Yellow A, Cerulein A, or the substantive dyes of the type Congo Red, or the azo dyes of the type Primulin, Aniline Yellow, Naphtol Blue Black B, Diamine Blue 23, Congo Blue, or the basic dyes represented by Rhodamine B, thiofiavine and aurarnine dyes or pigments of the type Hansa Yellow G, Toluidine Toner, or Copper phthalocyanine. Representative inorganic pigments include Lamp Black, Malachite Green, Iron Blue, Cadmium Yellow and the like.

In some instances, particularly in printing or Where the treatment of fibers with the film forming copolymer or the like and the particles of polytetrafluoroethylene is used chiefly to provide a base finish for subsequent treatment with coating materials or for printing or for other coloring compositions, the copolymer or the like may 300 F. to cure the percent by weight of the properly be dispersed in combination with the particles of polytetrafluoroethylene.

It will be understood that numerous changes may be made in the sequence of operations and the conditions thereof as well as in the formulations without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. Glass fibers the surfaces of which are coated with a composition containing polytetrafluoroethylene in finely divided form dispersed in a polymeric thermoplastic resinous film forming material and present in amounts ranging from 0.1-5 percent by weight of the polytetrafiuoroethylene and 0.2-25 percent by weight of the thermoplastic film forming resin.

2. Glass fibers the surfaces of which are coated'with polytetrafiuoroethylene in finely divided form dispersed in a polymeric thermoplastic resinous film forming material present in amounts ranging from 0.1-5 percent by weight of the polytetrafluoroethylene and 0.225 percent by weight of the thermoplastic film forming resin and a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains more than 10 carbon atoms coating the polytetrafluoroethylene coated glass fibers.

3. Glass fibers the surfaces of which are coated With the combination of a butadiene-acrylonitrile copolymer and polytetrafluoroethylene dispersed therein in finely divided form present in amounts ranging from 0.l-5 polytetrafluoroethylene and 0.2-25 percent by weight of the butadiene-acrylonitrile copolymer and a treating material on the surfaces of the coated fibers comprising a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains more than .10 carbon atoms.

4. Glass fibers and fabrics formed thereof coated with the combination of a film forming polymeric thermoplastic material and polytetrafiuoroethylene dispersed therewith in particle form and present in amounts ranging rem 0.1 to 5 percent by weight polytetrafiuoroethylene and 0.2 to 25 percent by weight of the .film forming material and a treating material insolubilized on the coated fibers comprising a Werner complex compound having an acido group coordinated with the trivalent nuclear chromium atom containing more than 10 carbon atoms.

5. Treated glass fibers and fabrics formed thereof as claimed in claim 4 in which the film forming material comprises a butadiene-acrylonitrile copolymer.

6. Treated glass fibers and fabrics formed thereof as claimed in claim 4 in which the film forming material comprises a resinous alkyl acrylate polymer.

7. Glass fibers coated with a film forming polymeric thermoplastic resinous material in which unfused particles of polytetrafluoroethylene are embedded and in which the materials are present in amounts ranging from 0.1 to 5 percent by weight polytetrafluoroethylene to 0.2 to 25 percent by weight of the film forming material.

8. In the method of treating glass fibers and fabrics formed thereof, the steps of coating the glass fibers after all previous coatings have been removed with an aqueous composition containing l25 percent by weight of a film forming polymeric thermoplastic resinous material and polytetrafluoroethylene in particle form dispersed therewith and present in the ratio of 0.1 to 5 parts by weight polytetrafluoroethylene to 0.2 to 25 parts by weight of the film forming material, and heating the coated fibrous structure at a temperature to fuse the film forming material into a continuous film but insufficient to fuse the particles of polytetrafiuoroethylene.

9. The method as claimed in claim 8 in which the film forming material comprises butadiene-acrylonitrile copolymer.

10. The method as claimed in claim 8 in which the film forming material comprises an alkyl acrylate polymer.

all previous coatings have been removed with an aqueous composition containing 1-25 percent by weight of a film forming polymeric thermoplastic resinous material and .polytetrafiuoroethylene in particle form dispersed there With and present in the ratio of 0.1 to parts by weight polytetrafiuoroethylene to 0.2 to 25 parts by weight of the film forming material, and heating the treated fibrous structure to a temperature Within the range of 300-350 F. to reduce the film forming material to a continuous film without fusion of the particles of'polytetrafiuoroethylene.

12. In the method of treating glass fibers and fabrics formed thereof, the steps of coating the glass fibers after all previous coatings have been removed with an aqueous composition containing 1-25 percent by weight of a film forming polymeric thermoplastic material and polytetrafiuoroethylene in particle form dispersed therewith and present in the ratio of 0.1 to 5 parts by weight polytetrafiuoroethylene to 0.2 to 25 parts by weight of the film forming material, heating the coated fibrous structure at a temperature to fuse the film forming material to a continuous film but insufiicient to fuse the particles of polytetrafluoroethylene, and treating the coated fibers with a 0.1 to 2 percent by Weight solution of a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains more than carbon atoms.

13. In the method of treating glass fibers and fabrics formed thereof, the steps of coating the glass fibers after all previous coatings have been removed with an aqueous composition containing 125 percent by weight of a film forming polymeric thermoplastic material and polytetrafiuoroethylenein particle form dispersed therewith and present in the ratio of 0.1 to 5 parts by weight polytetrafluoroethylene to 0.2 to 25 parts by weight of the film forming material, heating the treated fibrous structure to a temperature Within the range of 300350 F. to'reduce the film forming material to a continuous film without fusion of the particles of polytetrafluoroethylene, treating the coated fibers with a 0.1 to 2 percent by weight solution of a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains more than 10 carbon atoms, and then heating the fibrous structure to a temperature within the range of 300-350 F. for insolubilizing the complex.

14. In the method of treating siliceous, inorganic fibers, the steps of coating the fibers with an aqueous composition containing a film forming polymeric thermoplastic resinous material and polytetrafluoroethylene in'finely divided form dispersed therewith in amounts to provide the materials in the ratio of 0.1-5 parts by weight of polytetrafluoroethylene to 0.225 parts by weight of the film forming thermoplastic resinous material based upon the Weight of the coated fibers, and heating the coated fibrous structure at a temperature to reduce the thermoplastic material to a continuous film on the glass fiber surfaces but insufficient to fuse the particles of polytetrafluoroethylene dispersed therein. 7

15. In the method of treating siliceous, inorganic fibers,

. the steps of coating the fibers with an aqueous composition containing a film forming polymeric thermoplastic resinous material and polytetrafiuoroethylene in finely divided form dispersed therewith in amounts to provide the materials in the ratio of 0.1-5 parts by weight of polytetrafluoroethylene to 0.2-25 parts by weight of the film forming thermoplastic resinous material based upon the weight of the coated fibers, heating the coated fibrous structure at a temperature to reduce the thermoplastic material to a continuous film on the glass fiber surfaces but insufi'icient to fuse the particles of polytetrafluoroethylene dispersed therein, and treating the coated fibers with a solution of a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains more than 10 carbon atoms.

16. The method as claimed in claim 8 in which the previous coating on the glass fibers is removed immediately prior to the application of the thermoplastic resinous material and polytetrafluoroethylene by the step of heating the glass fibers at a temperature above 1050 F. but below the fusion temperature of the glass composition of which the fibers are formed immediately prior to the application of thethermoplastic resinous material and the polytetrafluoroethylene to effect the removal of previous coatings and to relax and weave set the fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,471,959 Hunt May 31, 1949 2,531,134 Kropa Nov. 21, 1950 2,539,329 Sanders Jan. 23,1951 2,552,910 Steinman May 15, 1951 2,604,427 Armstrong et al. July 27, 1952 2,604,688 Slayter July 29, 1952 2,633,428 Klug Mar. 31, 1953 FOREIGN PATENTS 490,877 Great Britain Aug. 23, 1938 

1. GLASS FIBERS THE SURFACES OF WHICH ARE COATED WITH A COMPOSITION CONTAINING POLYTETRAFLUOROTHYLENE IN FINELY DIVIDED FORM DISPERSED IN A POLYMERIC THERMOPLASTIC RESINOUS FILM FORMING MATERIAL AND PRESENT IN AMOUNTS RANGING FROM 0.1-5 PERCENT BY WEIGHT OF THE POLYTETRAFLUYOROETHYLENE AND 0.2-25 PERCENT BY WEIGHT OF THE THERMOPLASTIC FILM FORMING RESIN. 